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<head>
	<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
	<title>Document</title>
</head>
<body>
	<script type="text/javascript">
		//第一步，得到用户输入的成绩
		var score = parseFloat(prompt("请输入成绩"));

		//第二步，判断
		if(score >= 85){
			alert("优秀");
		}else if(score >= 70){
			alert("良好");
		}else if(score >= 60){
			alert("及格");
		}else{
			alert("不及格");
		}
	</script>
</body>
</html>